[1] Univ Edinburgh, Western Gen Hosp, Mol Med Ctr, Human Genet Unit, Edinburgh EH4 2XU, Midlothian, Scotland
[2] Royal Hosp Sick Children, Dept Paediat Neurol, Edinburgh EH9 1LF, Midlothian, Scotland
[3] Dundee Royal Infirm, Dept Neurol, Dundee DD1 9ND, Scotland